> S-2. The proper solution. > > Correct alignments for all partitions can't be achieved by the > firmware alone. The system utilities should be informed about the > alignment requirements and align partitions accordingly. > > The above firmware workaround complicates the situation because the > two different configurations require different offsets to achieve > the correct alignments. ATA/ATAPI-8 specifies a way for a drive to > export the physical and logical sector sizes and the LBA offset > which is aligned to the physical sectors. > > In Linux, these parameters are exported via the following sysfs > nodes. > > physical sector size : /sys/block/sdX/queue/physical_block_size > logical sector size : /sys/block/sdX/queue/logical_block_size > alignment offset : /sys/block/sdX/alignment_offset > > Let the physical sector size be PSS, logical sector size LSS and > alignment offset AOFF. The system software should place partitions > such that the starting LBAs of all partitions are aligned on > > (n * PSS + AOFF) / LSS > > For 4 KiB physical sector offset-by-one drives, PSS is 4096, LSS 512 > and AOFF 3584 and with n of 7 the above becomes, > > (7 * 4096 + 3584) / 512 == 63 > > making sector 63 an aligned LBA where the first partition can be > put, but without the offset-by-one mapping, AOFF is zero and LBA 63 > is not aligned. > > With the above new alignment requirement in place, it becomes > difficult to honor the legacy one - first partition on sector 63 and > all other partitions on cylinder boundary (255 * 63 sectors) - as > the two alignment requirements contradict each other. This might be > worked around by adjusting how LBA and CHS addresses are mapped but > the disk geometry parameters are hard coded everywhere and there is > no reliable way to communicate custom geometry parameters. Hello, I have practically no knowledge of Linux' block device drivers, but is this really a partitioning issue? I think the problem is with the filesystems when clustering multiple blocks without knowledge of the sector alignment and sector size of the underlying block device. Maybe it is a better solution to adapt the filesystem buffer routine which reads/writes data from/to the block device? Best regards Damian -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
